Right now, you can sign up to be a donor for free. (usually there is a fee to cover the costs of testing). They especially need minority donors because people are more likely to find a match within their own race, but they don't have a high percentage of minority donors in the registry.

This is an important issue to me because my sister was saved by a bone marrow transplant. She was fortunate to have a match within our family--out of 6 kids, only 1 of us was a match. Most people who need a transplant won't find a related donor, so that is why the registry is so important.